TY - JOUR
T1 - Iron mineral admixtures improve the sulfuric acid resistance of low-calcium alkali-activated cements
AU - Gevaudan, Juan Pablo
AU - Santa-Ana, Briana
AU - Srubar, Wil V.
N1 - Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2021/2
Y1 - 2021/2
N2 - We investigated the sulfuric acid resistance of low-calcium alkali-activated materials (i.e., geopolymers) supplemented with an iron mineral admixture (i.e., hematite). Geopolymers without and with 5% hematite were produced at two alkali contents (Na:Al = 0.86 and 1.39). Acid degradation reactions were comprehensibly studied through three replenishes of acid. Results demonstrate that hematite is chemically active upon acid exposure yielding a short-term increase in acid neutralization capacity. Prolonged acid resistance was enhanced in high alkali content formulations with hematite. Acid exposure revealed minimal changes to mineralogy, molecular structure, and micro-scale porosity in these samples, resulting in less dealumination and silicon leaching. Thus, results indicate that the acid buffering capacity of geopolymers, specifically at higher alkali content formulations, increases due to the addition of hematite. The increased buffering capacity leads to lower degrees of dealumination of the N-A-S-H cementitious binder. These results are important as they may help explain the increased acid durability of alkali-activated materials synthesized from industrial aluminosilicate precursors (e.g., slag, fly ash, lateritic clays) that may contain iron minerals.
AB - We investigated the sulfuric acid resistance of low-calcium alkali-activated materials (i.e., geopolymers) supplemented with an iron mineral admixture (i.e., hematite). Geopolymers without and with 5% hematite were produced at two alkali contents (Na:Al = 0.86 and 1.39). Acid degradation reactions were comprehensibly studied through three replenishes of acid. Results demonstrate that hematite is chemically active upon acid exposure yielding a short-term increase in acid neutralization capacity. Prolonged acid resistance was enhanced in high alkali content formulations with hematite. Acid exposure revealed minimal changes to mineralogy, molecular structure, and micro-scale porosity in these samples, resulting in less dealumination and silicon leaching. Thus, results indicate that the acid buffering capacity of geopolymers, specifically at higher alkali content formulations, increases due to the addition of hematite. The increased buffering capacity leads to lower degrees of dealumination of the N-A-S-H cementitious binder. These results are important as they may help explain the increased acid durability of alkali-activated materials synthesized from industrial aluminosilicate precursors (e.g., slag, fly ash, lateritic clays) that may contain iron minerals.
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U2 - 10.1016/j.cemconcomp.2020.103867
DO - 10.1016/j.cemconcomp.2020.103867
M3 - Article
AN - SCOPUS:85096847005
SN - 0958-9465
VL - 116
JO - Cement and Concrete Composites
JF - Cement and Concrete Composites
M1 - 103867
ER -